Method of reducing irritants in tobacco by gamma irradiation



Dec. 19, 1967 r H. v. BOENIG ETAL 3,353,694

METHOD OF REDUCING IRRITANTS IN TOBACCO BY GAMMA IRRADIATION Filed May11, 1965 i 3 I I '2 a I 1 l E N l 2 l n: E

2 g \\J I; i D O :2 *5 S I 2 O I v 2 l I a E i WAVELENGTH Herman .V.Boenig Winqafe A. Lambertson- Walter J. Braun Homer 5. Myers ATTORNE,

(%) HDNVilIWSNVHi United States Patent 3,358,694 METHOD OF REDUCINGIRRITANTS IN TOBACCO BY GAMMA IRRADIATION Herman V. Boenig, Wingate A.Lambertson, Walter J. Braun, and Homer S. Myers, Lexington, Ky.,assignors to the United States of America as United States Atomic EnergyCommission Filed May 11, 1965, Scr. No. 455,019 3 Claims. (Cl. 131-121)ABSTRACT OF THE DISCLOSURE A method modifying tobacco to produce lessirritants when burned comprising exposing it to at least one megarad ofgamma radiation.

Our invention relates to a method of treating tobacco to reduce theamount of irritants formed when it is burned.

Fresh tobacco smoke contains substances which are irritating and harmfulto body tissue. Attempts to remove these substances based on a step offiltering the smoke have had varying degrees of success. Filters whichare highly eflicient in removing tars make undesirable changes in thetaste of the smoke, and yet do not remove some irritants.

It has been discovered that fresh smoke from burned tobacco contains asignificant number of free radicals. As is well-known, free radicals arehighly reactive, and, consequently, their presence in tobacco smoke isundesirable since they may combine with other particles in the smoke toform harmful substances, or they may react directly with body tissue. Itis desirable to reduce the number of free radicals in fresh tobaccosmoke.

It is one object of our invention to provide a method of treatingtobacco to reduce the amount of irritants formed when the tobacco isburned.

It is another object to provide a method of treating tobacco to changethe substances produced during burning without making undesirablechanges in the taste of the smoke.

It is another object to provide a method of reducing the number of freeradicals in fresh tobacco smoke.

Other objects of our invention will be apparent from the followingdetailed description and the appended claims.

In accordance with our invention we have provided a method of treatingtobacco comprising exposing said tobacco to at least one megarad ofgamma radiation.

Tobacco treated in accordance with our invention burns to produce smokecontaining 25-30 percent less tar, about 50 percent less toluene, andabout 50 percent fewer free radicals than smoke from untreated tobacco.

The figure is an infrared analysis of the fraction of smoke condensatedistilling above 150 C. from non-irradiated and irradiated cigarettes.As can be seen by comparing the curve for the smoke from the irradiatedcigarette with the curve for the smoke from the non-irradiatedcigarette, irradiation has decreased significantly the amount of tarproduced upon burning tobacco.

While the mechanism by which irradiation of tobacco reduces the quantityof tars, toluene, and free radicals produced upon subsequent burning isnot known, and we do not therefore wish to be bound by any theory, it isbelieved that gamma radiation breaks some of the complex molecules intofragments which either remain in that form or combine with othermolecules or fragments. The result in either case is that the productcon-.

tains dilferent particles than did the untreated tobacco. These newparticles, being different, upon burning produce reaction products whichdifier from those produced by represented by the burning non-irradiatedtobacco. Unexpectedly, the products formed from irradiated tobacco areless irritating to body tissue than are the products formed fromnon-irradiated tobacco.

In carrying out our process the tobacco may be irradiated at any time inits processing from harvestinguntil after packaging for sale to theconsumer.

The quantity of radiation absorbed must exceed one megarad. A rad is ameasure of the energy absorbed per unit weight and is equal to 100 ergsper gram. A megarad is equal to 10 rads.

While the irradiation may be carried out to over 100 megarads, at thislevel the taste of the smoke produced on burning is adversely affected,and the dosage should be kept below 100 megarads, preferably from 5 tomegarads. The optimum dose is from 10 to 25 megarads.

The rate of irradiation is not critical and may be carried out fromrates of less than 0.1 to greater than 10 megarads per hour. Thelimitations of the radiation facility employed will normally fix theirradiation rate.

Having thus described our invention, the following examples are offeredto illustrate it in more detail.

Example I Cigarettes irradiated to a level of 10 megarads by irradiatingfor 10 hours at a rate of 1 megarad per hour and non-irradiated controlcigarettes were placed in a smoking machine designed to smoke 15cigarettes simultaneously. Each cigarette was smoked in turn, once eachminute. A puff consisted of a 35-milliliter intake of air over aZ-second period. The smoke was collected in a cold trap cooled with DryIce and propylene glycol. The collected smoke was washed from the traptwice with trichlorotrifluoroethane and three times with methylenechloride. The collected solutions were vacuum-distilled and thefollowing fractions were collected:

Fraction Vacuum Temperature 33 mm. Hg Room temperature to 50 C. 1 mm. Hg50 C. to 150 C. Remaining residu Infrared analyses performed on thesefractions showed that (1) in fraction 1 there were several compoundspresent in the smoke from non-irradiated tobacco which were absent insmoke from irradiated tobacco; (2) there was little difference betweenthe samples in the second fraction; and (3) the smoke from irradiatedtobacco showed a substantially smaller amount of all components in thethird fraction, i.e., the tars, compared to the smoke of non-irradiatedtobacco. The infrared analysis of the third fraction is given in thefigure. As can be seen from this figure the amount of tar in the smokefrom the irradiated tobacco is from 15% to 25% less than the amount inthe smoke from the non-irradiated tobacco.

Example II Cigarettes irradiated to a level of 10' megarads andnonirradiated control cigarettes were smoked in the smoking machine ofExample 1. Each cigarette was smoked at a rate of four puffs per minuteand milliliters of air was taken per putf. he smoke was trapped as inExample I, the condensate was dissolved in benzene and examined in anelectron spin resonance spectrometer within 15 minutes of collection.The relative signal intensities per milligram of condensate were 2.24-for the irradiated tobacco and 5.10 for the non-irradiated tobacco. Thisshows that the smoke from irradiated tobacco contained less than 50percent as many free radicals as the smoke from non-irradiated tobacco.

The above. examples are offered to illustrate and not to limit ourinvention. Modifications such as changes in irradiation time and dosemay be made Without departing from our invention.

Having thus clescribedour invention, we claim:

1. A process of treating harvested tobacco for the pnrposeofreducingvtars and free radicals comprising exposing it to at least onemegarad of gamma radiation.

2: The process, of claim 1 wherein the tobacco is itradiated'to a levelof: 5 to 75 megarads.

References Cited 5 UNITED STATES PATENTS 1,926,035 9/1933 Chesley3,142,759 7/1964 Jefferson et a1.

RALPH G. NELSON, Primary, Examiner. w A. B. CROFT, Assistant Examiner.

1. A PROCESS OF TREATING HARVESTED TOBACCO FOR THE PURPOSE OF REDUCINGTARS AND FREE RADICALS COMPRISING EXPOSING IT TO AT LEAST ONE MEGARAD OFGAMMA RADIATION.